1. Field of the Invention
The present invention relates to an image recording medium having a layer of color developer capable of color development by the reaction with a dye precursor encapsulated in microcapsules upon press development.
2. Description of Related Art
Photosensitive pressure-sensitive recording media have been known, such as: a self-contained type recording medium comprising a support having on the surface thereof microcapsules encapsulating a photocurable resin, a photopolymerization initiator and a dye precursor as main components, and a substance capable of color development (a so-called "color developer") by reacting with the dye precursor; and a separate-sheet type recording medium composed of a photosensitive sheet coated with photocurable microcapsules as described above and another separate sheet coated with a color developer (color developer sheet), as described, for example, in Japanese Patent Application (OPI) Nos. 23025/83, 88739/83 and 88740/83. (The term "OPI" means unexamined, published application).
These recording media utilize the property of microcapsules that become cured upon light-exposure due to the photocurable resin, etc. encapsulated therein. Such a recording medium is mounted on a device which effects the steps involving exposing the microcapsules to light in conformity with image information and rupturing unexposed and uncured microcapsules to bring the dye precursor encapsulated therein in contact with the color developer which is provided on the same surface of the recording medium or coated on another sheet, whereby a color-forming reaction occurs between the dye precursor and the color developer to form an image.
However, in the above-described systems, recording can only be effected on the specifically processed sheets, i.e., the photosensitive pressure-sensitive sheet or the color developer sheet but not on ordinary paper or other substrates such as cloth, PET film, etc.
A recording medium for solving the above problems is disclosed in Japanese Patent Application (OPI) No. 36482/89 which corresponds to U.S. patent application No. 07/184,096. This recording medium has a color developer medium which includes a base sheet made of polyethylene terephthalate, a color developer layer formed on the base sheet, and a thermoplastic resin layer formed on the color developer layer.
The manner of forming an image on ordinary paper is described with reference to the color developer medium. Initially, the ordinary paper and the thermoplastic resin layer of the color developer medium are superposed and heated, thereby causing the ordinary paper and the color developer to be bonded together. Subsequently, the base sheet of the color developer medium is removed thus forming a color developer layer on the surface of the ordinary paper. A photosensitive sheet which has been exposed to light in conformity with an image of an original and the color developer layer on the ordinary paper are then superposed and pressed by means of a press-developing device. By such pressing, uncured microcapsules on the photosensitive sheet are ruptured whereupon a dye precursor and the color developer react with each other, thereby forming an image conforming to the image of the original on the ordinary paper.
However, there are some materials on which no image can be formed when using the above color developer medium. More particularly, the above-described developer medium requires a pressing force exerted from the press-developing device as high as about 600 kg/cm.sup.2. The application of such a high pressure will break or deform certain kinds of materials such as glass, hard plastics and the like. Thus, no image can be formed on these types of materials with the above-described process. It is not possible to form clear images on some materials such as cloth which are not flat and are stretchable because a pressing force from the press-developing device cannot be uniformly applied.